Convert centimeters to diopters and back — no account needed
The furthest point where small text is still clear.
Negative means myopia (nearsightedness).
A diopter is the reciprocal of a distance in meters. If text goes blurry at 50 cm — half a meter — that is 1 ÷ 0.5 = 2 diopters of myopia, written as −2.00 D. The formula is just:
diopters = −100 ÷ (distance in cm)
This gives your spherical equivalent, which is an estimate — it does not account for astigmatism, and it is not a prescription. Your optometrist measures differently and will not always agree with this number. What it is genuinely good for is watching the trend in your own measurements over time, as long as you measure the same way every time.
| Diopters | Blur distance |
|---|---|
| -0.50 D | 200 cm |
| -1.00 D | 100 cm |
| -1.50 D | 66.7 cm |
| -2.00 D | 50 cm |
| -2.50 D | 40 cm |
| -3.00 D | 33.3 cm |
| -4.00 D | 25 cm |
| -5.00 D | 20 cm |
| -6.00 D | 16.7 cm |